Desalination using electrodialysis as a function of voltage and salt concentration

Electrodialysis is a process that competes with reverse osmosis for desalination and the removal of specific inorganic contaminants. Desalination experiments were carried out on aqueous solutions containing 5 and 10 g/L NaCl to determine the optimum operating conditions of an electrodialysis (ED) system. Further desalination of aqueous solutions containing 1, 5, 10, 20, 25 and 35 g/L NaCl at an optimum applied voltage of 12 V was conducted to determine the influence of initial salt concentration on the desalination process. The possibility of removing fluoride and nitrate from a groundwater containing about 4.3 g/L NaCl, as well as 2.8 and 31.3 mg/L of fluoride and nitrate respectively, as a function of applied voltage was also investigated. A laboratory electrodialysis stack containing seven cation-exchange membranes and six anion-exchange membranes of 56 cm2 effective area was used. From these studies it is demonstrated that electrodialysis is an effective method for the removal of fluoride and nitrate from brackish groundwater and that real groundwater showed a slower desalination behaviour. Fouling of the membranes was observed.